by Bart Jansen, USA TODAY

by Bart Jansen, USA TODAY

WASHINGTON - Transportation Secretary Ray LaHood vowed Friday that Boeing's 787 Dreamliner wouldn't take to the air again until regulators are absolutely certain it's safe.

"Those planes aren't going to fly until we are 1,000% sure that they are safe to fly," LaHood said outside a meeting of the U.S. Conference of Mayors here.

LaHood's comments came a week after he assured the public in a news conference with the Federal Aviation Administration (FAA) and plane maker Boeing that the planes were safe because of a robust certification process. He said Jan. 11 that he had no reservations about flying in a Dreamliner.

But following that assurance, an All Nippon Airways Dreamliner made an emergency landing on Wednesday after crew members smelled smoke from a smoldering lithium-ion battery on the plane.

All Nippon Airways and Japan Airlines, both of which fly the Dreamliner, grounded their planes, 24 in all, that day. The FAA later in the day ordered United Airlines to ground the six Dreamliners it has because of a series of problems, including a battery fire Jan. 7 in an empty Dreamliner at Boston's Logan Airport.

Following the FAA's action, other airlines around the world stopped flying their planes, too.

LaHood said regulators continue to work with Boeing engineers in investigating the batteries, the type of which Boeing uses to power systems only on the Dreamliner.

"The reason that we ground it was because we did further consultation with Boeing and there was another incident," LaHood said. "Those planes aren't flying now until we have a chance to examine the batteries. That seems to be where the problem is."

He said he couldn't say how long the review might last or when Dreamliners would fly again.

"We just have to be patient here," he said. "What the American people want is to fly on planes that are safe, and that's what we're going to assure them of.

"When there are incidents, it's our job to do the examination, to do the investigation, to do the review, to do it top to bottom. That's what we're doing."